The present invention relates to a liquid pressure control device for load responding brakes for automobiles for reducing output liquid pressure of a brake master cylinder at a predetermined ratio corresponding to a movable load and more particularly to improvement of a load sensing mechanism.
A liquid pressure control device of this type is disposed halfway in a liquid pressure passage leading to brake cylinders of rear wheels from a brake master cylinder, and applies braking force equal to that on front wheels to rear wheels at the time of low braking at the initial stage of braking and braking force smaller than that on the front wheels when the braking force reaches to a predetermined value or higher, thereby to prevent locking of the rear wheels. Further, since the magnitude of braking force produced by locking of the rear wheels is different depending on the weight of a movable load on a vehicle such as a truck, the braking force for starting to reduce the braking force to rear wheels is made larger when the movable load is large and smaller when it is small.
Namely, the liquid pressure of the brake master cylinder is reduced in the predetermined ratio and transmitted to brake cylinders of right and left rear wheels by opening and closing respective control valves by means of a pair of plungers responding independently with the liquid pressure from the brake master cylinder.
Furthermore, such an apparatus that, in order to give a characteristic according to a movable load of a vehicle to these control valves, the force according to a movable load is applied to respective plungers by means of a load sensing mechanism so as to change the pressure reducing action starting point (pressure) of the control valves, thereby to make the braking force control starting pressure of the rear wheels larger as the movable load is larger is already known. (For example, Japanese Utility Model Provisional Publication No. 63-148567 (No. 148567/1988)).
In a liquid pressure control device as described above, however, there has been such a problem that an equalizer for having force according to the movable load act on plungers of respective control valves interposes between a load sensing lever of a load sensing mechanism and above-mentioned respective plungers, action abutting points against respective plungers move against a large movement of the load detecting lever during assembly and adjustment as a device, and a plurality of parts and working thereof are also required in assembly, thus causing poor assembly workability on the whole.